Okay, I'll hash it out for you. Most of Miami's locker room is black. Incognito fit in better with them than Martin did. He understood their jokes better, he understood their ball busting better, he took it better and he gave it back to them better than Martin did. He was closer to them and they considered him a "brotha" because of that.
Martin, on the other hand, came from a different way of life. He came from Stanford and, as his own coach even admitted, was not used to the meathead personalities that came from places like Nebraska and LSU. He was well spoken and articulate, came from a more wholesome family background, and as such, had trouble relating to the meathead personalities that were in Miami's locker room. Now that the issue of supposed "racism" has been raised, because this country is way too PC and is too afraid to possibly insult someone, the Dolphins players are coming to Incognito's back because they related to him better on a personal level than "the Big Weirdo", hence the "he's one of us", type comments. It's not racism, it just is what it is.
That doesn't make Incognito a good person, Martin a bad person, and vice versa. It just means that Martin, personality wise, was a lesser fit in the locker room than Incognito.